In the graphic arts, it is desirable to produce a color proof to assist a printer in correcting a set of photomasks which will be used in exposing printing plates. The proof should reproduce the color quality that will be obtained during the printing process. The proof must be a consistent duplicate of the desired half-tone or line image, and should neither gain nor lose color. Visual examination of a color proof should reveal the following characteristics:
1. Any defects on the photomask. PA1 2. The best color rendition to be expected from press printing of the material. PA1 3. The correct gradation of all colors and whether grays are neutral. PA1 4. The need, if any, for subduing any of the colors and/or giving directions for altering the film photomask before making the printing plates. PA1 i) a colored, adherent, photosensitive layer, which layer comprises a light sensitive, positive working or negative working compound; a resinous binder and at least one colorant; and PA1 ii) an optional first colorless adhesive layer directly adhered to on said colored photosensitive layer, which adhesive layer has a softening point in the range of from about 60.degree. C. to about 180.degree.; and PA1 iii) an optional noncolored photosensitive or nonphotosensitive barrier layer coating between said colored photosensitive layer and said first adhesive layer said barrier layer being effective to prevent the intermingling of said colored photosensitive and optional first adhesive layers; and thereafter PA1 i) laminating said photosensitive member with heat and pressure to the optionally coated side of the temporary element; and removing said substrate from the photosensitive element by the application of peeling forces thus transferring the photosensitive member to the temporary element; and imagewise exposing said photosensitive layer to actinic radiation; or PA1 ii) imagewise exposing said photosensitive layer to actinic radiation; and laminating said photosensitive member with heat and pressure to the optionally coated side of the temporary element; and removing said substrate from the photosensitive element by the application of peeling forces thus transferring the photosensitive member to the temporary element; or PA1 iii) laminating said photosensitive member with heat and pressure to the optionally coated side of the temporary element; and imagewise exposing said photosensitive layer to actinic radiation; and removing said substrate from the photosensitive element by the application of peeling forces, thus transferring the photosensitive member to the temporary element; and
Color proofing sheets for multicolored printing have heretofore been made by using a printing press proof which requires taking all the steps necessary for actual multicolor printing. Such a conventional method of color proofing has been costly and time consuming. Color proofing methods have therefore been developed to simulate the quality of press proofs.
In the surprint type of color proofing method, a color proofing sheet is prepared by successively producing images of different colors from different color separation films onto a single receptor sheet. This is done by utilizing a single opaque support and by applying toners, photosensitive solutions or coatings of photosensitive materials of corresponding colors on the opaque support in succession. An example of this approach is described in U.S. Pat. No. 3,671,236. An advantage of the surprint type of color proof is that the color saturation is not influenced by superimposed plastic supports. This method more closely resembles the actual printing and eliminates the color distortion inherent in the overlay system.
Various processes for producing copies of an image embodying photopolymerization and thermal transfer techniques are known as shown in U.S. Pat. Nos. 3,060,023; 3,060,024; 3,060,025 3,481,736; and 3,607,264. In these processes, a photopolymerizable layer coated on a suitable support is imagewise exposed to a photographic transparency. The surface of the exposed layer is then pressed into contact with the image receptive surface of a separate element and at least one of the elements is heated to a temperature above the transfer temperature of the unexposed portions of the layer. The two elements are then separated, whereby the thermally transferrable, unexposed, image areas of the composite transfer to the image receptive element. If the element is not precolored, the tacky unexposed image may now be selectively colored with a desired toner. The colored matter preferentially adheres to the clear unpolymerized material. U.S. Pat. No. 3,574,049 provides a transfer process for printing a design on a final support which comprises (a) printing a design onto a temporary support, (b) superimposing the temporary support and the final support, (c) applying heat and/or pressure to the superimposed structure formed in (b), and (d) separating the temporary support from the final support which retains the printed design. The affinity of the design for the temporary support is lower than its affinity for the final support.
In U.S. Pat. No. 3,721,557 a method of transferring colored images is claimed which provides a stripping layer coated between the photosensitive element and the support. When the photosensitive layer is exposed to actinic light and developed, the more soluble portions are selectively removed to produce a visible image. The image-carrying support is pressed against a suitable adhesive coated receptor member and, subsequently, the carrier support sheet is stripped to accomplish the transfer of the image. A fresh layer of adhesive is applied to the receptor for each subsequent transfer.
One problem encountered in the production of color proofing images is that the transfer of the layers may only be made onto a specially treated final receptor sheet. That is, a color proofing film manufacturer will typically provide the customer with a special white receptor sheet to which the images are laminated. This receptor sheet firmly retains the laminated layers and yet allows the removal of temporary supports to which the colored photosensitive layers were previously attached. Such special receptor sheets have been necessary since they are able to withstand the multiple developing and laminating treatments required for a multicolor proof image. The required use of such special receptor sheet is disadvantageous to the printer and his customer since such do not permit the viewing of the multicolored proof on the paper stock which will actually be used for printing. The instant invention seeks to solve this problem by producing a color proofing system which in its final form is adhered to virtually any desired paper stock. Not only are diverse paper stocks usable, but one can use both sides of the paper and several small sample proofs can be sequentially laminated onto a larger sheet for layout analysis.